1. Filed of the Invention
This invention relates to the art of substrate micro-fabrication and, more particularly, to plasma assisted chemical vapor deposition chamber and processes.
2. Related Arts
Micro-fabrication of substrates is a well know art employed in, for example, fabrication of semiconductors, flat panel displays, light emitting diodes (LED's), solar cells, etc. various steps in micro-fabrication include forming thin film using various chemical vapor deposition (CVD) techniques. One such technique is generally referred to as plasma assisted vapor deposition (PECVD). Various chamber technologies have been used for PECVD fabrication, including microwave, inductive, and capacitive sources. In general, conventional chambers are designed so that power is delivered to the plasma from a source that is remote or opposite the substrate. For example, in inductive sources the coil is positioned above the roof of the chamber, while in capacitive sources the RF energy is generally applied to the anode embedded in the showerhead or ceiling of the reactor. The reasoning behind such design relates to preventing species bombardment of the substrate during deposition of the thin film.
Another feature of the prior art chambers is the use of remote clean. Since the chambers are used to deposit various materials on the substrate, the materials are also deposited on various parts of the chamber. One problem is that once the deposits on the chamber parts reach a certain thickness level, and partly as a result of thermal cycling of the chamber, the coating flakes off and generates particles that land on the substrate, thereby causing defects. Therefore, it is desirable to clean the chamber from such deposits. One method for cleaning the chamber is the use of plasma etching of the deposits. The most utilized method in the art is that of a remote plasma source, such as Astron®, available from MKS Instruments of Andover, Mass., Litmass® or available from Advanced Energy of Fort Collins, Colo. However, this solution requires attaching additional hardware to the reactor and activation of a plasma source separate from the reactor's source.
A recent problem encountered in the CVD art is that of “pinching.” Due to aspect ration of various structures that need to be CVD filled, as the material is deposited on the sides of the trench it closes the top so as to form voids inside the trench. This is shown in FIG. 1, illustrating trench 110 etched in substrate 100. As shown by contour lines 102, 104, and 106, as material is CVD deposited onto the substrate, it pinches at the top, 108, so as to form a seam or void 120. Even when a seam is generated, after an annealing step it often expands into a void. Such a void is undesirable as is considered a defect.